[Matty22]

To try and offer some assistance....
When i fret a C chord, i use the tip of my ring finger, on the A string 3rd fret, to lightly rest against the E string, to mute it if i strum it accidentally, you can do the same with the D chord....

Also, there are no concrete rules as to what fingers to put where. there are different ways to hold a chord, try swapping your fingers around, you may find it more comfortable, which will help with finger placement...